Field of the Invention
This invention relates generally to a solar control coating having one or more metal functional multi-film layers comprising at least one infrared reflective film and at least one absorptive film.
Technical Considerations
Solar control coatings block or filter selected ranges of electromagnetic radiation, typically radiation in the infrared region and/or ultraviolet region of the electromagnetic spectrum. These solar control coatings are pieced on transparencies, such as windows, to reduce the amount of selected ranges of solar energy entering a building. This reduces the heat buildup inside the building.
The solar heat gain coefficient (SHGC) is a measure of how well the coating blocks solar heat. The lower the SHGC, the more solar heat is blocked, i.e., the lower the solar heat buildup inside the building.
The light to solar gain (LSG) ratio is the ratio of the transmittance of visible light divided by the SHGC.
The overall heat transfer coefficient (U factor) is a measure of heat loss, e.g., through the window. The lower the U factor, the lower the heat transfer through the window, i.e., the higher the insulating level of the window.
While solar control coatings provide good solar insulation properties, it would be useful to improve the solar control properties of these coatings. For example, it would be useful to decrease the SHGC and/or to increase the light to solar gain (LSG) ratio.
To decrease the SHGC, the thicknesses of the infrared reflective metal layers could be increased. However, this would also make the solar control coating more reflective of visible light. Consumers prefer transparencies with high visible light transmittance but low visible light reflectance (both interior and exterior visible light reflectance). Further, increasing the thicknesses of the infrared reflective metal layers increases the sensitivity of the solar control coating to random or systematic variations in the thicknesses of the films making up the coating. This can alter or adversely impact upon the performance of the coating or the aesthetics of the coating. Additionally, increasing the thicknesses of the infrared reflective metal layers tends to decrease the durability of the coating to chemical and/or mechanical attack. Moreover, the accessible regions of the aesthetic/color space that are most broadly appealing and that can be reached using conventional solar control coatings employing one or more periods of dielectric/silver/dielectric structures, are constrained by the designs of conventional solar control coatings.
Therefore, it would be desirable to provide a solar control coating that provides enhanced solar control and/or aesthetic performance. For example, it would be desirable to provide a solar control coating having a low solar heat gain coefficient (SHGC) to prevent heat buildup inside of a building. For example, it would be desirable to provide a solar control coating having a high light to soar gain ratio (LSG). A high LSG indicates good solar heat blocking while allowing visible light to pass through the coating. This improves the natural lighting inside the building. For example, it would be desirable to provide a solar control coating having commercially desirable aesthetics and/or a larger available color space. For example, it would be desirable to provide a non-heat-treated solar control coating having one or more of the above advantages.